The béarnaise sauce is similar to the hollandaise sauce but is enhanced with shallots, tarragon, and vinegar. These two are the most celebrated of emulsified sauces and consist of a stable mixture of two liquids – vinegar or lemon and butter – that normally separate from each other. To keep them together they need an emulsifying agent that occurs naturally in many animal substances such as egg yolks (lecithin), milk (casein) and blood. In fact, a small quantity of casein in regular butter does, to a slight degree, help emulsify your hollandaise sauce. These agents work in three different ways: they coat the oil droplets, reduce water’s surface tension and give the oil droplets identical electrical charges.
So, the stability of an emulsion is threatened if:
- temperatures are too extreme (separates when frozen, curdles when heat reached 190°F)
- there is excess agitation – overbeating destabilizes the emulsion.
- a nasty thunderstorm strikes!
2 Tbsp of finely chopped shallots
1 Tbsp of red vinegar
1 Tbsp of water
1 Tbsp of fresh tarragon
3 large egg yolks at room temperature
1/4 tsp of salt and a pinch of cayenne pepper
1/2 cup (1 stick) of butter at room temperature and cut up in small pieces
- In a thick-bottomed saucepan mix the vinegar and the shallots.
- Cook on low heat until vinegar is evaporated.
- Add the water, the yolks, the tarragon, the salt and the cayenne.
- Beat with a whisk until just blended.
- Improvise a double boiler with 1/2 inch of water brought to a simmer in a large pan.
- Set the saucepan with the egg mixture in it.
- Cook for 1 or 2 minutes until yolks thicken.
- Beating constantly, gradually add increasing quantities of butter.